Hypodermic fluid dispensers fall into two broad categories, namely, needle hypodermic dispensers and jet injectors. Jet injectors are particularly useful in immunization programs which involve the delivery of a non-living virus; and needle injectors are useful in the delivery of non-living virus and of medications.
In general, jet inoculation, as compared to needle inoculation, is less traumatic, presents a lower risk of cross-contamination, requires less operator training, and allows a higher number of procedures per unit of time.
Although both needle hypodermic injectors and high pressure jet injectors have been widely used, the presently known devices have serious disadvantages. The problems associated with needle injectors in the spread of AIDS (Acquired Immune Deficiency Syndrome) alone is sufficient motivation to avoid proliferation of today's needle systems. People cannot be relied upon to dispose of needle injectors in accordance with instructions and good practice; and an element of the population are tempted to reuse needles without knowledge of or regard for safe practices.
Present hypodermic fluid dispensers are insufficient in that they do not administer large numbers of serum doses in veterinary and agricultural uses. Furthermore, those electrical dispensers used for portable applications involve the problem of transporting and disposing of depleted batteries.
Also, in veterinary and agricultural procedures, there is no concern for cross-contamination. If one of a group of animals gets ill, it is assumed that the entire group gets ill. Thus, for the injection of a group of animals, such as for the injection of BST hormone to a herd of cows, a single orifice can suffice.
Jet injectors generally avoid the above-referenced problems associated with needle injectors; however, the presently available injectors are expensive; prone to failure; too bulky, to transport conveniently; and are generally inconvenient to use.